The invention is directed to an electrically powered, hand-held screw driver with a housing, a depth stop arranged at the housing, a drive motor, an axially displaceable tool spindle operatively coupled with a tool holder, and a torque coupling, in the form of a claw coupling, which is arranged between the drive motor and tool spindle and has a coupling part on the motor side and a coupling part on the tool side connected with the tool spindle and fixed with respect to rotation relative to the spindle. The two coupling parts can engage with one another and the tool spindle is pretensioned or biased away from the motor-side coupling part by means of a coupling spring.
Hand-held screw drivers of the type mentioned above have the advantage that a certain screw-in depth for a fastener to be placed, for example, a self-cutting screw, can be adjusted by means of the depth stop. As soon as the depth stop contacts a surface into which the fastener is screwed, the two parts of the torque coupling are separated and the screwing-in process is halted.
DE 198 45 024 discloses a hand-held screw driver in which the torque coupling is formed by a claw coupling with engagement cams. The tool-side coupling part of the claw coupling is secured to the tool spindle in a positive engagement in axial direction. In this hand-held screw driver, as soon as the depth stop strikes the surface to be fastened during a screwing in process, the coupling part on the tool side, together with the axially displaceable tool spindle, is moved farther in the screwing-in direction relative to the housing by means of spring force. During this relative movement with respect to the housing, the tool-side coupling part is moved away from the motor-side coupling part until the two coupling parts disengage. The screwing-in process is stopped at this point.
This known procedure is disadvantageous because the motion of the tool spindle is carried out by means of the spring element and the separation of the two coupling parts is therefore carried out relatively slowly. In this way, the two coupling parts are moved together over a certain period of time in the manner of two ratchet elements, wherein the engagement cams are rotated relative to one another and accordingly strike one another repeatedly. This results in unpleasant noise and a high degree of wear on the coupling parts.